There is a long felt need for an economically viable process to convert acetic acid to ethanol and/or ethyl acetate. Catalytic processes for reducing alkanoic acids and other carbonyl group containing compounds have been widely studied, and a variety of combinations of catalysts, supports and operating conditions have been mentioned in the literature. The reduction of various carboxylic acids over metal oxides is reviewed by T. Yokoyama et al. in “Fine chemicals through heterogeneous catalysis. Carboxylic acids and derivatives.” Chapter 8.3.1, summarizes some of the developmental efforts for hydrogenation catalysts for various carboxylic acids. (Yokoyama, T.; Setoyama, T. “Carboxylic acids and derivatives.” in: “Fine chemicals through heterogeneous catalysis.” 2001, 370-379.)
A series of studies by M. A. Vannice et al. concern the conversion of acetic acid over a variety of heterogeneous catalysts (Rachmady W.; Vannice, M. A.; J. Catal. (2002) Vol. 207, pg. 317-330.) The vapor-phase reduction of acetic acid by H2 over both supported and unsupported iron was reported in a separate study. (Rachmady, W.; Vannice, M. A. J. Catal. (2002) Vol. 208, pg. 158-169.) Further information on catalyst surface species and organic intermediates is set forth in Rachmady, W.; Vannice, M. A., J. Catal. (2002) Vol. 208, pg. 170-179). Vapor-phase acetic acid hydrogenation was studied further over a family of supported Pt—Fe catalysts in Rachmady, W.; Vannice, M. A. J. Catal. (2002) Vol. 209, pg. 87-98) and Rachmady, W.; Vannice, M. A. J. Catal. (2000) Vol. 192, pg. 322-334).
Catalytic activity in for the acetic acid hydrogenation has also been reported for heterogeneous systems with rhenium and ruthenium. (Ryashentseva, M A.; Minachev, K M; Buiychev, B. M; Ishchenko, V. M.Bull. Acad. Sci. USSR1988, 2436-2439).
U.S. Pat. No. 5,149,680 to Kitson et al. describes a process for the catalytic hydrogenation of carboxylic acids and their anhydrides to alcohols and/or esters utilizing Group VIII metal alloy catalysts. U.S. Pat. No. 4,777,303 to Kitson et al. describes a process for the productions of alcohols by the hydrogenation of carboxylic acids. U.S. Pat. No. 4,804,791 to Kitson et al. describes another process for the production of alcohols by the hydrogenation of carboxylic acids. See also U.S. Pat. No. 5,061,671; U.S. Pat. No. 4,990,655; U.S. Pat. No. 4,985,572; and U.S. Pat. No. 4,826,795.
Malinowski et al. (Bull. Soc. Chim. Belg. (1985), 94(2), 93-5), discuss reaction catalysis of acetic acid on low-valent titanium heterogenized on support materials such as silica (SiO2) or titania (TiO2).
Bimetallic ruthenium-tin/silica catalysts have been prepared by reaction of tetrabutyl tin with ruthenium dioxide supported on silica. (Loessard et al., Studies in Surface Science and Catalysis (1989), Volume Date 1988, 48 (Struct. React. Surf), 591-600.)
The catalytic reduction of acetic acid has also been studied in, for instance, Hindermann et al., (Hindermann et al., J. Chem. Res., Synopses (1980), (11), 373), disclosing catalytic reduction of acetic acid on iron and on alkali-promoted iron.
Depending, for example, on market conditions, it may be desirable to control the relative amounts of ethanol and ethyl acetate that are formed in the catalytic hydrogenation of acetic acid. Thus, the need exists for processes and catalysts useful in controlling the type and relative amounts of the various products that are formed in the hydrogenation of acetic acid.